Physical activity is beneficial to children’s health and well-being. Evidence suggests that physical activity declines with age from childhood through adolescence and into adulthood, with boys being more active than girls at all ages. Physical activity participation in childhood is affected by the social support and role modelling provided by family, peers, friends, and teachers. Marginalized groups are disadvantaged in terms of access to opportunities to be physically active. From a population perspective, the greatest gains in public health will be achieved by helping those who are most inactive to become moderately active. Physical activity promotion efforts for children have predominantly focused on school-based programmes, but multisectoral approaches are needed with transformative and enlightened public policy regarding many facets of children’s lives such as school curricula, active travel, safe play areas, and enhanced sports opportunities for all.